A head-mounted image display device which is used when seeing and hearing an image by wearing the device at a head portion, that is, a head-mounted display has been known. The head-mounted image display device includes, for example, image display units for respective left and right eye, and is configured so as to control sight and hearing by using a headphone together. In addition, the head-mounted image display device is able to project images which are different in the left and right eyes, and to provide a 3D image when displaying an image with parallax in the left and right eyes.
It is also possible to classify the head-mounted image display device into a light shielding type and a transmission type. A head-mounted image display device of a light shielding type is configured so as to directly cover user's eyes when being mounted on a head portion, and a level of concentration of a user increases when seeing and hearing an image. On the other hand, in a case of a head-mounted image display device of a transmission type, since a user is able to see an outside view (that is, see through) beyond an image while displaying the image by mounting the device at a head portion, it is possible for the user to avoid a danger such as a collision with an obstacle when using the device outdoors, or while walking.
A lot of head-mounted image display devices are used for enjoying contents by being connected to an AV reproducing apparatus such as a DVD player, or a blue-ray disk (BD) player (for example, refer to PTL 1). Here, when seeing and hearing an image, it is necessary to instruct a user to turn volume up or down of a headphone, a start, a stop, fast forwarding, fast returning, or the like of reproducing contents with respect to a device.
For example, a head-mounted image display device to which a controller including a menu button for displaying a menu or deciding a selected item, an up button, and a down button for moving a targeted menu item, a volume dial for adjusting volume, and the like is connected has been proposed (for example, refer to PTL 2). However, a user wearing the head-mounted image display device is apt to perform an erroneous operation by fumbling for the controller, and treating the controller. In particular, in a case of the head-mounted image display device of light shielding type, since a user is almost in a blindfolded state, it is difficult to operate the controller.
Since the head-mounted image display device is in close contact with a user while being used, it is easy to obtain biological information of the user. By paying attention to the point, a try of performing an User Interface (UI) operation based on biological information which is measured from a user wearing the device has been performed. For example, it is possible to relatively easily obtain information on a movement of eyes of a user by making use of a device configuration such as a close contact with a head portion.
In the technical field, a method has been known in which eyes are photographed using a camera, and a movement of an eyeball, or blinking is caught using image processing. For example, a goggles type display which includes a line of sight input device performing a screen operation by detecting a reflection from an eyeball using infrared light, and detecting a position of a line of sight, or blinking, and performs a video reproducing operation, or an input operation of a personal computer without using a hand has been proposed (for example, refer to PTL 3).
However, the line of sight input device should be provided so as not to be an obstruction in a field of vision in the head-mounted image display device, and there is much limitation in a design and manufacturing. In addition, in particular, when it is a light shielding-type image display device, since an eyeball is photographed in an almost dark place, it is necessary to use a high sensitive camera when inputting a line of sight, and to perform high-definition image processing, accordingly, it results in an increase in cost of the device.
In addition, a head-mounted display in which a line of sight is detected by measuring an eye potential which is generated by a positive charge of a cornea and a negative charge of a retina using a plurality of electrodes which are attached to the periphery of eyes, that is, using Electro-Oculography (EGG), or the like has been proposed (for example, refer to PTL 4). However, an eye potential associated with a movement of an eyeball, a myogenic potential associated with blinking, and brainwaves are mixed in a potential difference signal which is input from the electrode, and it is necessary to treat them separately (for example, extracting only potential difference signal which is caused by blinking). In the head-mounted display, a rapid sacchadic movement of an eyeball at the time of moving of a position of a line of sight of a user is detected from an eye potential signal, and a steep change in a voltage which occurs due to blinking is eliminated.